Bank segment - Allowance for credit losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Allowance for credit losses:
Beginning balance	$ 71,130	$ 101,201
Charge-offs	(1,558)	(3,681)
Recoveries	1,402	1,308
Provision for credit losses	(3,763)	(7,035)
Ending balance	67,211	91,793
Real estate | Residential 1-4 family
Allowance for credit losses:
Beginning balance	6,545	4,600
Charge-offs	0	0
Recoveries	8	3
Provision for credit losses	1,321	658
Ending balance	7,874	5,261
Real estate | Commercial real estate
Allowance for credit losses:
Beginning balance	24,696	35,607
Charge-offs	0	0
Recoveries	0	0
Provision for credit losses	(4,520)	(1,262)
Ending balance	20,176	34,345
Real estate | Home equity line of credit
Allowance for credit losses:
Beginning balance	5,657	6,813
Charge-offs	0	(50)
Recoveries	11	15
Provision for credit losses	(18)	(877)
Ending balance	5,650	5,901
Real estate | Residential land
Allowance for credit losses:
Beginning balance	646	609
Charge-offs	0	0
Recoveries	5	10
Provision for credit losses	46	(46)
Ending balance	697	573
Real estate | Commercial construction
Allowance for credit losses:
Beginning balance	2,186	4,149
Charge-offs	0	0
Recoveries	0	0
Provision for credit losses	154	(2,696)
Ending balance	2,340	1,453
Real estate | Residential construction
Allowance for credit losses:
Beginning balance	18	11
Charge-offs	0	0
Recoveries	0	0
Provision for credit losses	13	5
Ending balance	31	16
Commercial
Allowance for credit losses:
Beginning balance	15,798	25,462
Charge-offs	(76)	(771)
Recoveries	353	273
Provision for credit losses	(1,761)	(460)
Ending balance	14,314	24,504
Consumer
Allowance for credit losses:
Beginning balance	15,584	23,950
Charge-offs	(1,482)	(2,860)
Recoveries	1,025	1,007
Provision for credit losses	1,002	(2,357)
Ending balance	$ 16,129	$ 19,740